After-treatment of acid-dyed cellulose acetate with salicylic acid



Patented Oct. 5, 1954 siren STATES PATENT OFFICE AFTER-TREATMENT OF ACID-DYED CELLU- LOSE ACETATE WITH SALICYLIC ACID Barbara Jane Weir, Wilmington, DeL, assignor to E. 1. du Pont de Nemours and Company, Wihnington, Del, a corporation of Delaware No Drawing. Application March 1, 1952, Serial No. 274,510

3 Claims.

pellicle and the like, for the great majority of I.

commonly employed dyes has been one of the major problems of the trade. This is commonly attributed to the fact that the cellulose acetate molecule has few available reactive groups. Yarns and fabrics produced from mixed fibers and filaments and containing cellulose acetate are particularly difiicult to process due to this dyeing problem. It is known in the art that cellulose acetate can be modified to increase its susceptibility toward various types of dyes. For instance, addition of 2 to of one or more non-cellulosic, non-proteinous, polymeric compounds containing amino nitrogen to the acetone solution from which the cellulose acetate is spun will render it suitable for acid dye application. Among suitable amino additives may be mentioned beta dimethylaminoethyl alpha methacrylate, beta diethylaminoethyl alpha methacrylate, triethanolamine monomethacrylate, 4- (beta methacrylyoxyethyl) morpholine and the like. The preparation of such acid-dye receptive cellulose acetate is described in detail in British Patent 480,297. Such modified cellulose acetate is commonly known as, and is referred to herein as, basic cellulose acetate. dyes are relatively inexpensive, are simple to apply, and have sufiicient afiinity for basic cellulose acetate, it has been found that they possess poor light-fastness when applied to this material.

In accordance with the present invention, an aftertreatment has been developed whichimproves the light-fastness of acid-dyed, basic cellulose acetate.

It is an object of the present invention to provide a process for the preparation of light-fast, acid-dyed, basic cellulose acetate.

Another object is to provide an acid-dyed basic cellulose acetate of improved light-fast characteristics.

These and other objects will become apparent in the course of the following specification and claims.

The aftertreatment of the present invention comprises contacting the dyed cellulose acetate products with a solution of salicylic acid.

While acid In accordance with the present invention, a basic cellulose acetate, in any form, such as a fiber, filament, yarn, fabric, pellicle or the like, is dyed with an acid dye and then subjected to a solution of salicylic acid. The nature of the solvent is not critical. However, to avoid spotting of the textile, it is preferred that the salicylic acid be completely in solution. Water is the most convenient solvent. Alcoholic or aqueous alcoholic solutions or other organic solvents which do not affect the textile or the dye may likewise be employed. In general, it is recommended that the treating solutions contain from 2.5 to 25 grams of salicylic acid per liter of solution employed. Where water is used as a solvent, it is necessary to heat the solution to with in a range of from about 160-2l2 F. to provide the proper solubility. Lower temperatures may be employed if a low salicylic acid concentration is used. Naturally, longer contact periods are necessary under these conditions. Higher temperatures, i. e., above the boiling point of the solution, may be employed provided suitable pressure is used to maintain the solution in the liquid state.

The method of applying the salicylic acid solution is not critical although care should be taken to obtain thorough and even distribution. Immersion, as by the use of a jig or beck is suitable. The treatment period, in each case, is related to the ease with which the structural configuration of the textile material to be treated permits proper coverage. Furthermore, the period of contact is related to the strength of the treating solution. For immersion in aqueous solutions, contact periods of from about 15 to 30 minutes are satisfactory in the higher concentrations of the range indicated above, to about to minutes in the lower concentrations. These values will Vary considerably, depending upon the physical characteristics of the material treated. It is not necessary to the stability of either the dye or the basic cellulose acetate that excess treating liquid be washed out. The ratio of textile weight to dyebath is not critical. It is convenient to use from 5 to times more liquid by weight than textile. The stabilizing solution can be applied to the dyed basic cellulose acetate after it has been dried, or while it is still moist from the dyeing step.

The nature of the acid dye is not critical. Many such dyes are known to the industry (Colour Index, edited by F. M. Rowe, published by the Society of Dyers and Colourists, Bradford, Yorkshire) Among such materials may be mentioned the sodium bisulphite salt of para-sulphobenzene-azo-beta-naphthol (C. I. 152), the toluenepara-sulphonyl esters (CI. 430), the sodium salt of the toluene-para-sulphonyl-ether of 4-pa1'ahydroxybenzene azo l para chloro orthosulpho phenyl 3 methyl hydroxypyrazol (C. I. 642), the sulphonic acids of dialkylaminophenylamino phenyl naphthophenazonium chloride (C. I. 833) and the sodium salt of 1:4 di ortho sulpho para tolylaminoanthraquinone (C. I. 1078).

The following examples are cited illustratively and not by way of limitation. The color fastness to light tests were made in accordance with tentative test method #16-45, described in the Technical Manual and Year Book of the AATCC, volume 26, pages 98, 99 (Howes Publishing Company, Inc., New York city, 1950). An FDA-P. Fade-Ometer, a carbon are fading lamp, manufactured by the Atlas Electric Devices Company, Chicago, Illinois, was employed as a source of artificial light. The specimens were exposed, one-half of the exposed area being covered with an opaque material, until the fabric being tested had faded slightly. After exposure, specimens were allowed to lie in a dark room at temperature for two hours. The samples were then classified relative to their fastness to light, as indicated in the test method.

EXAMPLE I A tubing knitted from a 150/48 cellulose acetate yarn which contains 5% of di-methyl amino ethyl methacrylate is dyed at 212 F. to a redviolet color in 40 times its volume of a neutral aqueous bath containing 0.5% on weight of fiber of sulfonated 2-an'1lino quinizarin acid dye. At the end of 30 minutes, a 28% aqueous acetic acid solution, which corresponds to 1% acetic acid based on fabric, is added. The dyeing is con-- tinued for another 30 minutes at 212 F. The fabric is then rinsed and dried. A 3 x 4 inch swatch is removed as a control and tested for light-fastness. Fading is observed in 4.5 hours. This corresponds to a fastness to light rating of L2.

The remaining unexposed fabric is then immersed for 5 minutes at 212 F. in 40 times its volume of an aqueous solution containing grams per liter of salicylic acid. Upon drying, a swatch is subjected to the light test described above. Fading occurred in 21 hours, corresponding to a fastness to light rating of L5.

Following the general procedure outlined in Example I, a series of dyeings is made on similar yarn employing various dyes as indicated in Table I.

4 Table I Example Dye Color Yellow.

Violet.

Yellow.

'lliiodlphenyl-pp-dls-azo-bis salicylic acid 1:5-dl-ortho-sulpho-para-tolylaminoanthmquinone (C. I. 1,080).

Sodium salt of the toluene-para-sulphonyl ether of 4-para-hydro:q'benzcnc-azrrlpara-chloro-ortho-sulpho-phenyl-S-methyl- 5-l1ydroxy-pyrazol (C. I. 642). I

Table H Time to Fading Festness to Light (Hours) Rating Examples Aftcr- After- Control Treated Contiol Treated 3. 5 19 L2 L4 4.0 18 L2 L4 4. 5 19 L2 L4 While the process has been described with particular reference to basic cellulose acetate, it is applicable as well to other cellulose esters which have been modified to improve receptivity of acid dyes such as, for instance, cellulose propionate, butyrate, the mixed esters, the chloroform soluble tri-esters and the like where similar light-fastness problems are encountered.

Many equivalent modifications will be apparent to those skilled in the art without a departure from the inventive concept.

What is claimed is:

l. A process for the treatment of cellulose acetate which has been rendered acid dye sensitive by incorporating in it polymeric di-methyl amino ethyl methacrylate, which comprises dyeing the said cellulose acetate with an acid dye and thereafter contacting it at 212 F. for about at least 5 minutes with an aqueous solution containing about 15 grams of salicylic acid per liter of solution to render it light-fast.

2. The process of claim 1 wherein the cellulose acetate is in the form of a yarn.

3. The process of claim 2 wherein the acid dye is sulphonated 2-anilino quinizarin acid dye.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,168,337 Heckert Aug. 8, 1939 2,376,891 Alles May 29, 1945 

1. A PROCESS FOR THE TREATMENT OF CELLULOSE ACETATE WHICH HAS BEEN RENDERED ACID DYE SENSITIVE BY INCORPORATING IN IT POLYMERIC DI-METHYL AMINO ETHYL METHACRYLATE, WHICH COMPRISES DYEING THE SAID CELLULOSE ACETATE WITH AN ACID DYE AND THEREAFTER CONTACTING IT AT 212* F. FOR ABOYT AT LEAST 5 MINUTES WITH AN AQUEOUS SOLUTION CONTAINING ABOUT 15 GRAMS OF SALICYLIC ACID PER LITER OF SOLUTION TO RENDER IT LIGHT-FAST. 